Device for casting by centrifugal force



Feb. 27, 1934. J. LEUSER 9, 1

- DEVICE FOR CASTING BY CENTRIFUGAL FORCE Filed July 19, 1932 INVENTO R Josef L euser GE K @M- ATTORNEY Patented Feb. 27, 1934 UNITED STAT S PATENT OFFICE,

Josef Leuser, Pforzheim, Germany, assignor to Deutsche Goldund Silber-Scheideanstalt,

vormals Roessler, Frankfort-on-the-Main, Germany, a corporation Application July 19, 1932, Serial No. 623,437 In Germany July 25, 1931 60laims.

The present invention relates to improvements in centrifugal casting machines such as are principally used by the dental profession in casting inlays, crowns, bridges and the like, and its object is to present a machine in which the charge which consists chiefly of precious metals is fused and then forced by centrifugal force into the mold which rotates around a vertical or a horizontal shaft. V t

In the casting industry generally the metal or alloys after they have been fused in crucibles are poured into separately kept molds. Thus products are obtained which as regards the low requirements which are asked of the precision of the article formed are quite satisfactory. In the production of such casts as are used in the dental professiomthe application of special means are necessary to obtain casts which show all the details of the molds and which are absolutely true reproduction of-all the parts of the article to be moulded. For some time past it has been customary in the production ,of such castings to use centrifugal forces, pressure or suction to transfer the fused metal into the mold in the desired manner and to distribute it therein satisfactorily.

. The fusion itself was hitherto carried out with 4 an open flame, for instance, by means of a blow pipe which, as a rule acts directly on top of the mass of the mold itself. For this purpose little grooves or cavities were cut into a part. of the mold and were connected through one or more channels with the cavity proper of the mold. Thus after the casting metal was fusedby means of an open flame the fused metal was run into the mold. by its own gravity. Further, it has been old to use devices in which little pans or crucibles, for instance of clay, were mounted adjacent the casting mold. The metal or the alloys were fused in these devices with an open flame and afterwards were projected into the mold by pressure such as by rotation of the like.

In practice all these devices produced a considerable number of failures which could be traced to the influence of the open flame upon the metal or the alloys respectively to be fused. It was found that the casting material was easily overheated and picks up oxygen from the surrounding air or from the flame itself when exposed diitself. This is specially noticeable in alloys conized in particular by the fact that the chamber in which the fusion is carried out, is formed by a crucible which excludes the direct contact with the flame and which has the shape of a pipe and which in addition, consists advantageously of car- 'bon. The equipment is so arranged that the mold after the metal has been fused with an open flame is rotated around avertical pivot. Preferably the fusion crucible is provided with a central opening which allows the fused metal to pass therethrough, while the fusion chamber i. e. the crucible is mounted airtight directly on the opening in the mold. In this way the fused metal passes into the mold without'hindra'nce whereby perfectly sound products are obtained. As the fusel metal enters the mold only when the centrifugal force has attained a certain acceleration, a rapid introduction into the mold is secured which does not leave any residue in the crucible and projects the fused metal into the finest and remote recesses and crevices of the mold.

The crucible acting as melting chamber is preferably in the shape of a pipe and by this shape excludes direct contact withthe flame.

Its contents of metal or alloy is liquefied by the influence of the flame upon its walls. These crucibles are made according to my invention from materialswhich like carbon prevent a deterioration of the fused goods. Crucibles of carbon have the special advantage that the buming carbon particles consume the oxygen 'of the surrounding air whereby it is possible to do away with the addition of de-oxidizing agents.

My invention is illustrated in the accompanying drawing, forming part of this application which shows various forms of the arrangement according to my invention.

Fig. 1 shows a casting device in which 'a closed fusion crucible and. the casting mold are vertically disposed. 1

Figs. 2 and 3 are enlarged vertical sections of the fusion room proper as it is mounted on the rotatable structure.

In particular according to Fig. 1 the structure b, b is arranged to rotate around the axle a. At the free end of the structure bis arranged the carrier 0 with the bottom plate at which can be turned as a whole. On the latter is fixed the mold e. The crucible which is mounted on top of the casting mold and which consists, for instance, of a carbon crucible, has such a shape, that the contact of the casting material with the open fiame is prevented. The crucible rests with its bottom so that the opening I lies over the entering channel of the mold. It is mounted in a device 9 with the aid of which its distance from the mold may be fixed at will and which if desired can be turned round the joint h. A counterbalance weight 2' is arranged on the part of the structure I). This can be screwed tightly in any one of a number of positions and permits the arrangement to be evenly balanced when rotated about the axle a. The sliding weight 2" mounted on the structure b is moveable between the crucible closed. m is a protecting shell, made for instance of asbestos. It is fixed on the carrier c.

The application of my device is as follows:

The crucible, the aperture of which is closed by a rod 2, is heated externally with a blow pipe until its metal or metal alloy content is fused. The crucible is then mounted by means of the handle n and device 9 (which carries the crucible) and which is connected to said handle directly on the mold e and the device given a rotatory movement. As soon as a certain speed is attained the weight 2" slips away from the centering pivot and withdraws by means of the chain it the rod Z from the aperture and allows the fused mass to be projected into the mold. The device is kept rotating until the whole of the fused mass has again solidified.

According to Fig. 3, the mold e" is mounted at the outer end of a carrier which is connected with the pivot u and is placed against the footplate 2; which is adjustably moveable on the carrier. The pipelike crucible-which is made, for instance, of carbon is mounted in such a way that its distance from the mold may be varied. It can, however, be joined as tightly as possible on to the mold. This crucible protects the material to be fused from contact with the heating flame. Its inner space is shaped in such a way that the material to be fused lies at a certain distance below the aperture f so that only when a certain speed of the carrier t is attained the centrifugal force becomes high enough to throw the fused good over the steep wall w through the aperture .1" into the cavity of the mold. The crucible is surrounded by a refractory lining a: which serves in a certain way as heating cham ber when the crucible is heated.

What I claim is:

1. A centrifugal casting device comprising a carbon crucible in the form of a substantially cylindrical tube and adapted to contain a charge of metal, said crucible being closed at one end and provided at said end with an aperture, means for normally preventing molten metal from passing through said aperture, a mold having an opening adapted to communicate with said aperture, said crucible and mold being mounted on a rotatable support for relative movement towards and away from each other, said crucible being formed to permit heating only from the outside.

2. A centrifugal casting device comprising a carbon crucible in the fomi of a substantially cylindrical tube and adapted to contain a charge of metal, said crucible being closed at one end and provided at said end with an aperture, means for normally preventing molten metal from passing through said aperture, a mold having an opening adapted to communicate with said aperture, said crucible and mold being mounted for relative movement towards and away each other, said crucible being formed to permit heating only from the outside, and means to prevent heating of said crucible when it is in contact with said mold.

3. A centrifugal casting device comprising a rotatable support, a mold mounted on said support, a fixed distance from the axis of rotation, a

-metal from passing through said aperture, said crucible being mounted on saidrotatable support for movement towards or away from saidmold, whereby said crucible may be heated at a point remote from said mold.

4. A casting device, comprising a support mounted for rotation about an axis intermediate its ends, a mold carried by a portion of said sup port to one side of said axis, a crucible mounted adjacent said mold and provided with anaperture connecting the interior of said crucible with said mold, an element normally closing said aperture, and means controlled by a predetermined centrifugal force operating on the other side of said support when the device is rotated about said axis for removing said aperture closing ele ment from said aperture.

5. A casting device, comprising a support mounted for rotation on an axis intermediate its ends, an adjustable counter-balancing weight mounted on one side of said support, a slidable weight mounted on said side between the axis and said counter-balancing weight, tensioning means for maintaining said slidable weight in normal position, a mold carried by the other side of said support, a crucible for molten metal positioned adjacent said mold and provided with an aperture connecting the interior of the crucible with said mold, a rod normally closing said aperture, and means connecting said rod to said slidable weight.

6. In a casting device, a supporting structure mounted on an axle intermediate its ends, a carrier mounted on one end of said supporting structure, a mold and a crucible supportably carried by said carrier, said crucible being adapted to be heated from the outside and provided with an aperture at its outer end connecting with said mold, the other end of said supporting structure having an adjustable counter-balancing weight thereon, a slidable weight mounted on said last named end between said counter balancing weight and said axle and maintained in normal position JOSEF LEUSEB. 

